Speed governor



Feb. 16, 1943. F. w. MERRILL 2,311,409

' SPEED eovmmon Filed Dec. {5, 1941 2 Sheets-Sheet 1 Inventor-z Frank W.Merrill,

- His Attorne g.

Feb. 16, 1943. F. w. MERRILL 2,311,409

SPEED GOVERNOR Filed Dec. 3'. 1941 2 Sheets-Sheet 2 Va n55 amass Fig.5.sown/10R warmers w/nmur .sma/uzm 6'0 CYCLE FER SECWVD TIM/N6 WIWE WIT/lSTAB/LIZER 6'0 CYCLE PER SECflA/D TIN/1V6 WAVE Ifiventor':

Frank W. Merrill,

His Attorneg.

Patented Feb. '16, 1943 2,311,409 srna'n GOVERNOR Frank W. Merrill, FortWayne, Ind., assignor to General Electric Company, a corporation of NewYork Application December 3, 1941, Serial No. 421,436

8Claims.

This invention relates to speed governors and more particularly tocentrifugally operated speed governors of the center contact type.

By center contact governor is meant a governor having a rotatable membercarrying a contact which is mounted concentrically with respect to itsaxis of rotation and which is actuated by means of centrifugal weightsso as to movein an axial direction. This so-called center contactcooperates with a fixed contact for opening and closing a speed controlcircuit. The position of the fixed contact is usually adjustable in theaxial direction so as to provide adjustment of the speed setting of thegovernor. Thus, depending upon the position of this flxed contact, theamount of centrifugal force and hence speed required to move the centercontact against the opposing action of the spring will be varied. Thegovernor may be embodied in a number of forms, some of which are shownin Tiffany Patents Nos. 1,136,739 and 1,303,417 and also in Ulmer PatentNo. 1,795,240 and Sole Patent No. 1,860,556; All of those governors arecharacterized by the use of a transversely flat blade spring whichcarries the center contact and which also carries one or more actuatingweights which serve to bend the spring longitudinally under theinfluence of centrifugal force. This spring is usually made of steel andit may either be normally straight as in the 'I'iflany patents ornormally curved, the curve being either concave inwardly as in the Ulmerpatent or convex outwardly as in the Sole patent.

he most common use of such a governor is as an automatic speed governorfor an electric motor in which case the contacts are connected, eitherdirectly or indirectly through an amplifier, in either the motorarmature circuit or the moto. field. circuit. t serves to compensate forovations in motor load, motor supply voltage anti motor temperature. 111 these variations norrnahy tend to vary the speed of a motor, thetemperature variation causing variation in resistance of the motorwindings which in turn varies the current in them and hence the speed.

For ordinary variations in these quantities of a few per cent theregulator operates very satisiactorily to maintain constant speed.However, over a great voltage range, such as a range of 2 or more to 1,typically from 350 volts to 150 volts, combined with load changes, orover a very wide adjustable speed range such as 4 to 1, typically 8,000R. P. M. to 2,000 R. P. M. combined with load changes on the motor ithas been found that the governor becomes unstable and what may be termedrough in operation. In order that the governor be able to maintainconstant speed under such wide variations in operating conditions it isnecessary that its contacts be able to control a relatively large amountof power, either directly or by means of a suitable amplifier. In eithercase the power impulses established by the opening and closing of theregulator contacts are so great that any deviation from their normalsteady vibratory beat will cause great surges in the valve of the inputcurrent to the motor. With a direct current motor these surges act likea superposition of alternating current on the otherwise direct currentinput and cause abnormal losses and poor commutation.

. I have found that this unstable or rough oper ation and itsaccompanying power surges may be eliminated by the addition of what Icall a stabilizing weight or weights to the center contact springassembly. These stabilizing weights are so mounted that their center ofgravity lies the spring and center contact to sudden jumps or movementsin a manner to spring so that it has a fluttering action interferes withthe natural steady vihr" tion or the center contact. The stem. weights,however, act like a top or gyrosc produce relatively powerful effectprevent the spring from twisting so c to move its center part out ofparallelism with its nor= mal plane of rotation.

In addition to their the gyroscopic effect the stabilizing weights alsohave a straightforward intertia effect which in many instancessubstantially improves the governor action. For example, without thestabilizer weights a con ter contact regulator cannot regulate motorswith heavy rotors without violent hunting. 'ihis is because theregulator is so much faster mm the inertia response of the motor rotorthat the governor contacts will close and remain closed for a largepercentage of the cycle, and then open suddenly and remain open forquite a long time while the rotor is responding to the impressed changeof flux. When the stabilizer weight is added it slows the period of thespring moving back and forth in an axial direction. After this issufficiently slowed, the spring takes up a vibratory motion which fitsin with the heavy inertia of the motor rotor and good regulation isobtained.

An object of the invention is to provide a new and improved speedgovernor.

Another object of the invention is to provide novel stabilizing meansfor centrifugal speed governors of the center contact type.

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawings and its scope will bepointed out in the appended claims.

In the drawings Fig.1 illustrates a side view of a regulator embodyingmy invention in which the governor casing is partly broken away to showits construction; Fig. 2 is a perspective view of the rotating memberand-center contact assembly of the governor; Fig. 3 is an oscillogram ofthe voltage across the governor contacts without my stabilizer, and Fig.4 is a similar view with my stabilizer.

Referring now to the drawings in which like reference numerals designatethe same parts in the two views, the regulator comprises a rotatablemember I which may be made of any suitable material and which is adaptedto be mounted on the end of a shaft 2, such as the shaft of an electricmotor, a part of the housing of which is shown at 3; Mounted on therotatable member is a transversely flat longitudinally curved spring 4which is preferably made of suitable spring steel. The ends of thisspring are fastened by any suitable means, such as rivets, to theperiphery of the rotatable member in such a way that the spring extendsacross the axis of rotation of the rotatable member. As shown, thespring is curved so as to be concave inwardly as viewed from left toright in the drawings. Fastened to this spring'd by any suitable means,such as rivets, are actuat ng weights 5 which are located near the endsof the spring and on opposite sides of its center. Carried at the centerof the spring and mounted concentrically with respect to its axis ofrotation is a center contact 6 which cooperates with a normally fixedbut axially adjustable contact I carried on the end of a threaded screwb which is turned by means of a knurled knob 9. Electrical connectionsare made to the center contact through the spring 4 by means of acollector ring ill on the rotatable member and a brushassembly IIcarried by a housing 82.

The stabilizing means for the governor comprises a thin blade or bar I3carried by the spring 4 and mounted transversely thereon by means ofrivets l4. At the extremities of this bar are stabilizing weights IS.The center of gravity of the weights l5 lies substantially in the planeof rotation of the center part of the spring 4 so that the centrifugalforce produced by these weights produces a gyroscopic effect whichstabilizes the plane of rotation of the center part of the spring 4 andhence prevents fluttering of the spring and theturning of the face ofthe center contact out of its normal plane of rotation which isperpendicular tothe axis of rotation. I

It has been found that when the stabilizer bar I3 is riveted flatagainst'the convex side of the spring 4 it sometimes causes a slightspring distortion which interferes with the best operation of thegovernor. In order to overcome this small washers are interposed betweenthe surfaces of these elements and the small side rivets and largecenter contact rivet pass through them. The spacing provided by thesewashers leaves the spring free to move freely and regulate in its usualmanner.

The electrical connections to the stationary center contact are made bya'spring l6 and connector H.

The operation of the illustrated embodiment of the invention is asfollows: As the rotatable assembly increases its speed the centrifugal Iforce developed in the weights 5 bends the spring 4 ,so as to movethecenter contact 6 toward the fixed contact I. This action is of courserestrained by the spring. At a predetermined "speed the contacts touchthereby completing an electric circuit which by well-known means can becaused to reduce the speed of rotation of the shaft 2. As soon as thespeed is reduced slightly the contacts separate whereby the speed isagain increased. In this manner the contact 6 has a vibratory motion inthe axial direction.

The stabilizing Weights E5 on the cross-bar i4 exert equal and balancedtension on the bar as the speed increases but have no direct ef-' feeton thefunction of the actuating weights. There is an. indirect effect,however, due to the inertia of these weights which must not beoverlooked. This is beneficial up to a'certain point in reducingvibration frequencies in an axial direction higher than the fundamentalestablished by the time constant of the fields and the inertia of therotor; but the stabilizer weights must not be made so heavy as to slowthe vibration period below this fundamental frequency or the accuracy ofthe regulation will be seriously affected.

In Fig. 3 an oscillogram of the voltage across the governor contactswhen the governor is not provided with my stabilizing means is comparedwith a sixty cycle per second timing wave. The regulated device was athree horsepower cross armature reaction excited direct armaturereaction compensated motor. As will be seen by a comparison of thecurves, the contact frequency was about 7 cycles per second.Furthermore, the voltage range is relatively wide resulting in a largemodulation of the power of the regulated motor thereby producingobjectionable surges and disagreeable noise. Fig. 4 shows the effect ofadding my stabilizing means. No other changes were made. This resultedin such an increase in frequency of the governor contacts .that thetiming wave has been shown stretched out so as to make easier acomparison between the two curves. parison, the governor contactfrequency has increased to about cycles per second and the amplitude ofthe contact voltage has been substantially reduced. Furthermore, thecontact voltage wave is much more regular when the stabilizer is presentthan when it is absent.

While there have been shown and described a particular embodiment ofthis invention, it will be obvious to those skilled in the art-thatvarious changes and modifications can be made therein without departingfrom the invention and, therefore, it is aimed in the appended claims tocover all such changes and. modifications as fall within the true spiritand scope of the invention.

Aswill be seen by such com- What I claim as new and desire to secure byLetters Patent of the United States, is:

1. A centrifugal speed governor of the center contacttype comprising, incombination, a re tatable member, a transversely flat steel springmounted on said member and extending longitudinally across the axis ofrotation of said member with the portion of its flat side which is inthe vicinity of said axis being perpendicular to said axis, a centercontact mounted on said spring concentrically with said axis, anactuating weight mounted on said spring for bending it under theinfluence of centrifugal force so as to move said center contactaxially, stabilizing weights mounted on said spring on opposite sides ofsaid center contact for holding the face of said spring in the vicinityof said center contact perpendicular to said axis by virtue of theirgyroscopic effect, and a fixed contact for cooperation with said centercontact.

2. A centrifugal speed governor of the center contact type comprising,in combination, a rotatable member, a center contact, means comprising atransversely fiat steel spring for supporting said contact on the axisof rotation of said member, the portion of said spring in the vicinityof said center contact being in a plane which is substantiallyperpendicular to said axis of rotation, stabilizing means for saidportion of said spring comprising a transverse member fastened to saidportion of said spring at a pin" rality oi spaced points and extendingoutwardly therefrom in both directions in said. plane, and stabilizinweights fastened to the ends of said transverse member and acting underthe infiu= ence of centrifugal force to produce a gyroscopic effecttending to prevent said portion of said spring from deviating fromparallelism with said plane of rotation.

3. A centrifugal speed governor of the center contact type comprising,in combination, a rotatable member, a center contact, means comprising atransversely fiat steel spring for supporting said contact, on the axisof rotationof said member, the portion of said spring in the vicinity ofsaid center contact being in a plane which is substantiallyperpendicular to said axis 01' rotation, means including actuatingweights carried by said spring on opposite sides of said portion of saidspring for bending said spring under the influence of centrifugal forceso as to move said center contact axially, a fixed contact forcooperation with said center contact, stabilizing means for said portionof said spring comprising a transverse member fastened to said portionof said spring at a. plurality of spaced points and extending outwardlytherefrom in both directions in said plane, and stabilizin weightsfastened to the ends of said transverse member and acting under, theinfluence of centrifugal force to produce a gyroscopic eflfect tendingto prevent said portion of said spring from deviating from parallelismwith said plane of rotation. r

4. A stablized center contact centrifugal speed regulator comprising, incombination, a rotatable member, a transversely flat blade spring, means.for fastening the ends of said spring to said member on diametricallyopposite sides of the lines axis of rotation thereof, said spring beingbent longitudinally so that the center part thereof at said axis ofrotation and predetermined points thereon on opposite sides of said axisof rotation lie in different planes of rotation, weights fastened tosaid spring at said points whereby the eiTect-of centrifugal force onsaid weights as said member rotates about its axis of rotation is tobend said spring so as to move its center part toward the plane ofrotation of said weights, a contact mounted on said spring at its centerpoint, a fixed contact for cooperation with said spring carried contact,means for stabilizing said spring comprising a transverse memberfastened to said spring at its center part and lying in its plane ofrotation, and weights fastened to said transverse member on oppositesides of said center part whereby the effect of centrifugal force onsaid last-mentioned weights is to produce a gyroscopic effect tending tostabilize the direction of the plane of rotation of the center part ofsaid spring.

5. In a centrifugal speed regulator of the center contact type, a fixedcenter contact, a rotatable cross bar assembly comprising a transverselyfiat longitudinallycurved steel spring, a substantially straight barfastened crosswise to the center of said spring, a second center contactmounted at the intersection of said spring and bar for era-operationwith said fixed center contact, a pair of actuating weights mount-ed,iacent the ends of said spring and a pair of stabilizing weightsmounted adjacent the ends oi said bar,

6.. The combination as set forth in claim 5 wherein said spring and barare of substantially the same length and said actuating and sta bilizingweights are of substantially the same size.

7. A vibratory contact speed governor for electric motors comprising, incombination, a contact which is normally fixed with respect to saidgovernor, a contact for co-operation therewith which is normallyvibrated relative to said governor, a spring for urging said normallyvibratory contact in one direction, means including a centrifugallyactuated weight for urging said normally vibratory contact in theopposite direction, and a stabilizing weight attached to said normallyvibratory contact for increasing its inertia in the direction of itsvibratory motion without varying the centrifugal force on it in thedirection of its vibratory motion.

8. A stabilized center contact speed governor comprising, incombination, a rotatable contact, a normally fixed contact forco-operation with said rotatable contact, means for vibrating saidrotatable contact in its axial direction into and out of engagement withsaid fixed contact including a centrifugal weight for urging saidrotatable contact in one direction and a spring for urging it in theopposite direction, and means for increasing the natural period ofvibration of said rotatable contact comprising an additional weightattached to said rotatable contact so that the centers of gravity ofsaid rotatable contact and said additional weight coincide.

FRANK W. MERRILL.

